It is proposed to investigate the dynamic mechanical response of an in vivo long bone to mechanical impact and attempt to develop this into a clinical tool for quantitative measurement of the state of healing of a fracture in the bone. A mathematical model of human and animal tibia will be developed which will predict the response of an accelerometer pressed against one end of the tibia due to a measured force on the opposite end. The model will then be used to predict the fracture stiffness of fractures in human tibias. If successful the technique will be put into clinical use.